Direct carbonization of polymer materials has been widely verified as a method for preparing carbon materials. The advantage of this approach is that it can obtain various forms of carbon using various polymer materials or patterns (e.g., block copolymer assemblies, patterns, or polymer spheres) as a precursor. Further, compared with using soft or hard templates for fabrication of porous carbon, the direct carbonization is more simple and easy. Specifically, the carbonization of photoresist polymer patterns is well established and enables a lithography-based design of carbon materials which is one of the highly delicate microfabrication techniques. The fabrication of micropatterned carbons has been successfully demonstrated and has led to new applications of carbon materials in MEMS, electrochemical sensors and energy devices.
Polymer carbonization is typically processed at high temperatures (usually 500° C. or more) to induce pyrolytic reduction of the polymers into carbonaceous materials. This high-temperature treatment of polymer patterns may result in the following problems. (1) Firstly, the polymer may flow, for example, at a glass transition temperature (Tg) of the polymer or higher and the polymer pattern morphology can be changed to lower the surface energy, which makes it difficult to obtain a desired carbon pattern. (2) Further, a large mass loss during carbonization at a high temperature may also lead the shrinkage of the macroscopic morphology of the produced carbon. Conventionally, such macroscopic morphology changes were reported less frequently. This may be mostly attributed to the use of template materials for fabrication of porous structures. The template maintains the structure during the carbonization. Moreover, most of the lithography-patterned polymer patterns used for direct carbonization are thin and film-like. In this case, strong adhesion with a substrate may resist macroscopic pattern change during carbonization. However, an attempt to utilize polymer films with high-aspect-ratio or high-specific-area patterns (e.g., three dimensional or porous patterned film) in direct carbonization may be more likely to encounter this problem. For example, a photoresist polymer pattern with a three dimensional pore network and submicrometer features was prepared and the morphology thereof during a heat treatment was investigated. It was found that the polymer patterns flowed out and then induced pore collapse at only 150° C. (much lower than the carbonization temperature), resulting in pattern-collapsed carbon films. Therefore, a method for improving the thermal stability of polymer patterns may first be required to maintain the structural integrity during the direct carbonization.
Korean Patent No. 10-1356791 discloses a film-type supercapacitor and a method of fabricating the same.